Weave Exposure - ️️Surface condition of a base material in which the unbroken
fibers of woven glass cloth are NOT completely covered by resin.
Haloing - ️️condition existing in the base material in the form of a light area around
holes or other machined areas on or below the surface of t...
IPC-A-610 Test
Weave Exposure - ✔️✔️Surface condition of a base material in which the unbroken
fibers of woven glass cloth are NOT completely covered by resin.
Haloing - ✔️✔️condition existing in the base material in the form of a light area around
holes or other machined areas on or below the surface of the base material.
Mechanically induced fracturing or delamination on or below the surface of the base
material; a Light area around the holes, other machined areas or both.
(a light ring around a hole on a circuit board)
3 types of Conformal Coating: Silicone Resin (SR) - ✔️✔️This type of coating provides
EXCELLENT protection in a very wide temperature range. This coating provides good
chemical resistance, moisture, and salt spray resistance, and is very flexible. This type
is NOT abrasion resistant because of its rubbery nature, but this property does make it
resilient against vibrational stresses. Commonly used in high-humidity environments.
Removal can be CHALLENGING. requiring specialized solvents, long soak time, and
agitation from a brush.
3 types of Conformal Coating: Urethane (Polyurethane) Resin (UR) - ✔️✔️This type of
coating is known for its EXCELLENT moisture and chemical resistance. It is also very
abrasion resistant. Combining those factors with its SOLVENT RESISTANCE results in
a conformal coating that is very difficult to remove. Like SR, full removal generally
requires special solvents, long soak time, and agitation with a brush. This is common in
aerospace application. ex: Conathane
3 types of Conformal Coating: Acrylic Resin (AR) - ✔️✔️This type of coating provides
FAIR elasticity and general protection. It has high dielectric strength, and fair moisture
and abrasion resistance. This coating is different from others because its facility for
removal. This type are EASILY and quickly removed by a variety of solvents, often
without requiring agitation. This makes rework and field repair very practical and
economical. This type doesn't protect against solvents and solvent vapors.
5 Coating application methods: Manual Spraying - ✔️✔️Aerosol can or handheld spray
gun. Time consuming method of coating for a small quantity of boards. Lots of masking
beforehand. Quality and consistency of outcome are operator- dependent.
5 Coating application methods: Automated spraying - ✔️✔️Programmed spray system
that moves the board on a CONVEYOR under an alternative spray head that applies a
conformal coating.
, 5 Coating application methods: Selective coating - ✔️✔️An automated conformal
coating process that uses PROGRAMMABLE ROBOTIC SPRAY NOZZLES to apply
the coating to very specific areas on the circuit board. May eliminate the need for
masking using the program. The UV lamp in machine helps cure the coating right after it
is sprayed.
5 Coating application methods: Dipping - ✔️✔️The circuit board is first immersed, Then
withdrawn from the conformal coating solution. Immersion speed, withdrawn speed,
Immersion time, and Viscosity determine the resulting film formation. Common for high
volume processing. Masking may increase. This method is good to coat both Front and
Back of the board.
5 Coating application methods: Brushing - ✔️✔️Simple application method used mainly
in repair and rework. Conformal Coating is applied with a BRUSH to specific areas on
the board. Low-cost method but requires lots of manual labor and is highly variable
depending on operator proficiency and consistency. This is the best for a small batch or
a single board.
1. Solvent Removal
2. Peeling
3. Microblasting: using a concentrated mix of soft abrasive and compressed air to
abrade the coating.
4. Grinding/Scaping - ✔️✔️What are the Conformal Coating Removal Methods by IPC?
(4)
(6) Most Common Coating Defects and causes:
Capillary Flow - ✔️✔️occurs when coating migrates from one area of a board to
another, leaving behind an inconsistent, uneven finish on the surface.
Causes: -application of too much coating
- coating with low viscosity or high surface tension.
- low surface energy of component being coated.
(6) Most Common Coating Defects and causes:
Cracking and Ripples - ✔️✔️Visual cracks and creases on components.
Causes: -coating is too thick
- thermal shock
- coating cured too quickly
(6) Most Common Coating Defects and causes:
Dewetting - ✔️✔️Coating will not evenly coat the surface to which its applied.
Causes: - uneven coating application.
- improper mixture of two- part material.
- Residue on coating surface.
- Surface tension and surface energy.
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